How to repitch your own impeller

[PolarisNut]

I see that the Yamaha and Sea-Doo guys have their own thread on this, and figured it would be a good addition to the Polaris side. I'm going to be repitching a couple of my Nu Jets here in the next couple of days and will be posting pics along with a how to. I already redid one and was rewarded with exactly the rpm I was looking for. Once I get the Nu Jets done, I'm going to work on a Skat for my rough water setup. For me, it's not so much the money to have someone else repitch it, but the hassle of shipping it, and being down for a week and a half. Plus, I always like learning something new. Jay from Atlantic gave me a few decent pointers along with the courage to take my first stab. Thanks Jay! I printed out the pitch gauge from Beerdart on some transparency film, and it worked great. Ideally I'd have the gauge from Randy though, but I'm cheap. Anyone else, please feel free to chime in.

[octanemad]

good on you, let us know the results.

OM

[CrazyA]

I'm going to sticky this for a while!!!


c

[PolarisNut]

I'm going to sticky this for a while!!!

c

Dang, now I'm under pressure, LOL.

[rlharrison60]

Im Listening, Tell us something. You can always teach a old dog new tricks.

[PolarisNut]

I'll try to get the pics up so they make sense. I'm certainly no expert, and I'm still learning, but thought I'd share so maybe a few others would be inclined to give it a shot.


This shows the visual differences between stock and modified


This shows the weld/casting flash that needs to be cleaned up to help the hookup. I used a die grinder with a 3" cutoff wheel attached to get in the tight spot, then cleaned it up with a stone, and then a sand roll. The idea here is to make the transition as smooth as possible. The ground area needs to be feathered into the untouched area. If done correctly, it makes a significant difference.


Here is what it should look like when done.


Stock pitch with my make-shift impeller gauge.


I use a 12" crescent wrench. I put the jaws about halfway on the blades about 1" up from the bottom. Give it some strong pressure. I then move the wrench another 1/2" up the blade and give it a little pressure there too. The idea is to have a smooth transition all the way down the blade. You dont want any sudden changes that will cause cavitation and inefficiency. You also want to make small changes at first until you get the feel for how much pressure it will take to make the bend take. The stainless steel springs back a bit more than I was expecting.


This shows a very slight pitch change, but the main point of this pic is to show how to mark the impeller before repitching begins. I place the gauge at the trailing edge of the impeller, and then mark the impeller where the gauge goes off the edge. Then after tweaking it, I have two points to line it up again, to be sure that I am getting an accurate measurement of the new angle.

More to come later as I do a few more. I have to test this one to see how much RPM I drop. Once I get it to the rpm I want, I'm going to send it out to Impros to have them give it a once over and a consistent finish. I may try to media blast it later and see how it comes out.

[rlharrison60]

I have some good impellers ill donate for the cause.

[Keddano]

Any updates?

[PolarisNut]

Any updates?

Well, I've been delayed by my drive shaft woes. As soon as I get my new shaft (he he), I'll be back at it. I was shown an easier way to tweak the nu-jets than what I did before and I'll be posting that soon.

[ph2ocraft]

Something that I have always wondered.
How is ti that you can use a wrench to change the impeller pitch BUT the water won't change it over time?
It just seems that if you can bend a crank and break pistons that the water could bend or take the impeller out of shape.
I know there's nothing on the back side of the blade to compress the water but daaaamn.

Patiently waiting as well...now where could those damn parts be.

[CrazyA]

Something that I have always wondered.
How is ti that you can use a wrench to change the impeller pitch BUT the water won't change it over time?

It's because of MA, or Mechanical Advantage. The wrench becomes a lever so-to-speak, one of the six basic tools which are comprised of:

Lever
Wheel & Axle
Pulley
Inclined Plane
Wedge
Screw

m

[timmy_philson]

Hi guys, mind if i ask for a copy of the pitch gauge where i can print it? Thanks guys.

[ph2ocraft]

It's in the tech section.

[timmy_philson]

polarisnut, mind if i ask from you the pattern for the impeller pitch gauge?

[beerdart]